1. Field of the Invention
The present invention relates to optical connectors.
2. Discussion of the Related Art
Coupling optical elements, such as Vertical Cavity Surface Emitting Lasers (VCSELs), with optical fibers is a relatively difficult, time consuming, and expensive task. One reason for this is that optical coupling requires precise physical alignment between the optical fiber and the optical element. Complicating the problem is that the physical alignment must remain accurate over both time and temperature. For example, when coupling an optical element to a single mode optical fiber a physical alignment that is accurate within a micron or so radially, and between 10 and 15 microns axially, over the full temperature range and over the life of the product can be required.
Optical connectors are used to couple optical fibers to optical elements. A primary task of an optical connector is to couple optical signals between elements with minimal signal loss. As previously noted, an optical connector must provide for precise physical alignment in the axial and radial directions. Various physical alignment techniques have been tried with varying degrees of success. Prior art approaches include molded lens coupling, butt coupling, and butt coupling with V-groove alignment. While generally successful, such prior art methods are, as stated, relatively difficult and expensive to implement.
Compounding physical alignment problems is the need for plug-in connectors that can be made and unmade numerous times, all while meeting the required alignment precision. In practice, to minimize signal losses stemming from imprecise radial alignment, most plug-in type optical connectors relay light from a first optical element, such as a VCSEL light source, into a single mode fiber (SMF) stub. That SMF stub is terminated, polished, and inserted into a split sleeve. The SMF stub is usually comprised of a ceramic material having a coefficient of thermal expansion that closely matches the coefficient of thermal expansion of the optical fiber. The SMF stub is often captured by a split sleeve assembly within an optical connector such that the plugged-in optical fiber is accurately positioned relative to the end of an optical fiber that is fixed within the SMF stub within the optical connector. Conventionally, any radial movement during plug-in is taken up by the flexibility of the split sleeve. In practice, the split sleeve is optically coupled to the optical element via a conventional butt or lens-coupling technique.
While the SMF stub is amenable to batch ferrule assembly and polishing, it is a small and relatively delicate part that can be difficult to handle in automated machinery. Thus, the SMF stub approach does not provide an economical solution to precision optical alignment of an optical element with an optical fiber.
Therefore, a new optical coupler would be beneficial. Even more beneficial would be a new optical coupler that enables accurate alignment of optical elements. Still more beneficial would be a new optical coupler having an optical receptacle that enables plug-in connections that accurately align an optical element relative to an optical fiber. Beneficially, such a plug-in optical coupler would include an optical receptacle that provides zero clearance tolerance for the radial alignment of an optical element relative to an optical fiber over time and temperature. Preferably, such an optical coupler would be low-cost and useable by relatively untrained assembly workers.